Circuit arrangement for the blocking of circuits in interlocking plants operating with electric lockings



April 2, 1957 R. HELMERT CIRCUIT ARRANCEMENT FCR THE: BLCCKINC CF CIRCUITS IN INTERLOCKING PLANTS OPERATING WITH ELECTRIC LOCKINGS Filed April l5, 1953 ROBERT HELMERT INVENToR.

gy/aw )L ATfoRNY United States Patent ice CIRCUIT ARRANGEMENT FOR THE BLOCKING F CIRCUITS IN INTERLOCKHNG PLANTS OP- ERATING WITH ELECTRC LGCKINGS Robert Helmert, Stuttgart, Germany, assigner to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application April 15, 1953, Serial No. 349,@44

Claims priority, application Germany April 19, 1952 2 Claims. (Cl. 317-436) Trafc control machines with electric interlocking necessitate a preventive arrangement for eliminating a simultaneous action of several switching operations. So, for instance, certain routes should not be lined up simultaneously, or signals should not be made to display a clear aspect at the same time. Under certain conditions the simultaneous throwing of a number of switches must be prevented. When all these operations are, as usually, controlled by relays, rest contacts of all other relays in eonicting circuits are connected into the circuits of these control relays so that each relay disconnects all other relays when responding. This system, however, requires a large number of contacts and the entire circuitry becomes badly arranged and is liable to faults due to the complication of the system.

As an improvement, the present invention provides for feeding circuits of switching relays, simultaneous response of which shall be prevented, over the coils of a common blocking relay which reverses the circuits by its response so that no further switching relay can be energized. When the reverse results in the interconnection of a resistor into the common link of the circuit, there is only one Contact of the blocking relay required for this function.

The coils oi the switching relay and of the blocking relay are suitably so designed that the switching relay responds rst when being operated and then the blocking relay, while upon a simultaneous connection of several switching relays, the blocking relay responds lirst and thus prevents the response of the switching relays.

When a circuit is established and is also to be guarded against ground connections and stray currents, the individual circuits of the switching relays are fed at both ends via a blocking relay each, as a further example of this invention, whereby cach of these blocking relays actuates the blocking function upon response. For supervising the action of the blocking relays, contacts of these relays are incorporated in the circuits controlled by the switching relays.

A better understanding of the invention may be had from the description of specific examples thereof made in connection with the copending drawing, in which;

Figure l is a schematic circuit diagram of an embodiment of the invention using a single blocking relay and Figure 2 is a modified circuit arrangement in accordance with the invention utilizing two blocking relays to provide additional controls.

Turning rst to Fig. l, two parallel operated circuits are shown, one of which includes an auxiliary relay Sl and a utilization relay Fi, the other one of which is provided with similar relays S2, F2. A blocking relay A is connected in common to these parallel circuits. lt should be understood that more than two such parallel circuits may be provided but only two are illustrated for the purpose of simplicity. Furthermore, it is to be understood that these utilization relays are the ones which control signals or switches related to conflicting routes so that only one such circuit may be established at any 2,787,740 Patented Apr. 2, 1957 one time. Two separate switches T1, T2 are shown in the energizing leads for switch relays Si, S2 respectively. As illustrated, these switch contacts T1, T2 show the lines open at this time.

Closure of switch Tl, for example, completes a circuit from the source of positive voltage through the winding ot relay A, back contact all, common lead C1, winding ot auxiliary relay S1, resistor Wi, contacts Tl to ground, causing relay Si to be energized and to operate. Relay A is a marginal relay requiring greater current than can be drawn through the single lead and resistor W1 in order to operate. @poration of relay S1 closes a circuit through the shunting lead around resistor W1 at contact s11 shcrting out this resistor thereby passing suicient current to operate relay A. Operation of relay S1 also closes contacts S12 in the circuit of relay F1 but this relay still does not operate since its complete circuit is still open at 112, when relay A operates however, Contact cl2 com pletes a circuit for relay F1 from positive potential source, Contact m12, contact slZ, winding of relay F1 to ground. This relay then controls signalling equipment or operates switches to give a clearance for a particular track circuit. At the same time relay A serves to operate contact all to open its direct energizing path but alternative energization for relay A is maintained from positive through. the winding of relay A, resistor Wa, winding of S1, contact all, contact T1 to ground. Resistor Wa is or' such a resistance value that it reduces the current passing through the relay windings A and Sl, but will not pass suliicient current to operate any further switch relays but `will maintain them energized once operated, Since the maintaining current is considerably less than that required to actuate the relay.

if contact T2 had been closed instead of Tl then relays S2 and F2 would have been operated through the precisely similar circuit for this relay including common conductor Cl, including the relay contacts S21 and S27.,

Relay A, while marginal in operation, is designed to be quicker operating than relay S1 or S2. Should contacts T1 and T2 be simultaneously closed then relay A will operate before either or" relays Sl or S2 operate, since sufficient current will pass through the parallel connected e resistances W1 and W2 and the windings S1, S2 to energize relay A. Upon operation of relay A, contacts all will open thereby removing the short circuit from resistor Wa so that relays Si and S2 will now receive insuicient current to operate them since their operating paths may now be traced from positive, winding of relay A, resistance Wa, winding of relay Si, resistance W1 and the parallel path from conductor C1 through the winding of relay S2 through resistance W2. Thus there is provided a safety interlock which prevents simultaneous display of signals through the operation of both circuits, since if neither of the relays S1 or S2 can Operate, the control relays Fl or F2 cannot operate since their operating paths include a set of the contacts on the S1 or S2 relays, namely slZ or S22. This arrangement provides a circuit which effectively locks out all other S relays after the operation of any one of them.

In Fig. 2 a slightly modified alternative circuit is shown which provides the same protection against simultaneous operation of signals but additionally provides an arrangement to take care of other possible faults which may develop in the system. ln the arrangement of Fig. 2, the control switches for the two separate paths are T11 and Till; for the circuit, including common leads C2, C3, relays S1 and Fi, and switches T21 and T22 for the alternative circuit including relay S2 and relay F2. In addition, a slow operating relay B is also provided common to the two circuits and suitable contacts b11, b12 are provided in the common branch circuits for relays meme@ Sl, S2 and relays F1, F2 respectively. A normally open bridging circuit is provided across the normally closed contacts bll and a short circuiting connection shunts resistor Wa. A switch-over contact all operated by relay A is provided upon `operation to close the shunt path around contact bll to open the shunt contact aro-nd resistor Wa. In order to set lup the circuit for Sl, Fl, contacts Til and T12 are operated to close the circuit. Immediately upon closing these contacts an operating circuit is set up for relay Sl from the positive voltage source, winding of relay A, closed contacts all, the shunt connection around resistor We, common lead C2, line Ll, closed contacts Til, line L2, winding relay Si, resistor' W1, winding of relay i3 to ground. Operation of relay Sl Closes switch contacts all short circuiting out resistor Wl so sutiicient current will now dow through winding to enable relay A to operate and also closes coL t: sli in the circuit of relay Fl. Relay Fl, however, cannot operate since its energizing circuit is still open at blt2 The short circuiting of resistor Wl supplies and @12. suicient current to operate relay A, which then operates at contact all. to short circuit out contact bil and to open the circuit around resistor Wn at the front contact all. Operation of relay A also closes switch contact 112 but since the operating circuit for relay El is stili open at blZ it still does not operate. After operation of relays 1 and A, relay B operates due to its slower response, and closes its contact bZ so that relay Pl also operates. Simultaneous operation of switches Til, T21, T32 and T22 will serve immediately to operate relay A in the same manner as described in Fig. l preventing setting up of either of the circuits.

in addition to the blocking feature against setting up conieting routes the second common relay i3 also serves to protect against the establishment of signals due to various faults which may occur in the signalling circuit. Should any ground occur between relay A and the normally open switches T11; and T21 relay A will immediately operate inserting resistor Wa via its contact all, so that neither relays S1 nor S2 can operate. A stray voltage introduced into line Li will provide an opposing voltage to the positive voltage of A preventing operation of relay A by effectively short circuiting it. Accordingly, neither F1 nor F2 can operate since contact cl2 will not close. Any stray voltage introduced into line L2 will operate both relays Sl and B, the operation or" contact bil `then will cut ott relay A so neither relays Pl nor F2 can respond. Should a fault occur interconnecting Ll and L2, relay F1 cannot operate since its circuit is still opened at contact blt2.

lt will thus be apparent that this system provi es protection against any type ot faalt as well as protection against setting up of conicting routes due to improper operation of the switches.

While )j have described above the principles ot my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention, as set forth in the objects thereof and in the accompanying claims.

What-is claimed is:

l. An interlocking electrical control system for a plurality of utilization relays comprising a plurality of auxiliary relays corresponding in number to said utilization relays, common blocking relay means, a plurality of impedances, one for each of said auxiliary relays and said blocking relay means, a source of operating potential, a plurality of switch elements, each element adapted .to control a different one of said auxiliary relays, each of said auxiliary relays and said blocking relay means havener n windings and a plurality of contact sets controlled thereby, a plurality of separate series circuits including different ones of said auxiliary relay windings, said impedances and said switch elements, a further series circuit including the energizing Winding of said blocking relay means er' another of said impedances, said separate series circuits in parallel series relation with said further series circuit across said source, a contact set of each of said auxiliary relays connected in a manner to shunt its associated impedance upon energization of the winding thereof, a contact set of said blocking relay means norr ally connected in shunt with its associated impedance, a plurality of additional series circuits for operating each of said utilization relays, each including another normally open contact set of a different one of said auxiliary relays, each of said additional series circuits in parallel relation with the other and in series with other normally open contact means of said blocking relay means across said sourc the response characteristics of said blocking relay means being such that the current passing through said further series circuit is insuicient to operate said blocking relay means until the impedance in thc series circuit connected therewith is shunted by operation of the associated auxiliary relay, and the characteristics of said ar., iliary relays being such that the current passing through said farther series circuit after operation of said blocking relay means and an auxiliary relay is insufficient to operate a second auxiliary relay.

2. An interlocking electrical control system as claimed in claim l, wherein said blocking relay means comprises a pair of blocking relays each having a winding connected in said further series circuit, a rst one of said blocking relays having a slow response characteristic and having normally closed and normally open contact sets, said second blocking relay having a transfer and normally open contact sets, the normally open contact sets of both said blocking relays connected in series with said additional series circuits, the normally closed contact set of said tirst blocking relay serially connected between the Winding of said second blocking relay and said other irnpedance, the transfer contact of said second blocking relay connected to shunt other impedance in its back position and to shunt the normally closed contacts of said rst blocking relay in its front position.

References Cited in the file of this patent UNITED STATES PATENTS 2,162,911 Crago M lune 20, 1939 2,375,413 Guenther May 8, 1945 2,633,487 Dawe Mar. 3l, 1953 

